1. Field of the Invention
The present invention relates to lift chairs and more particularly relates to an improved elevator or "lift" chair apparatus for use by invalids, and wherein the chair has a lower base with a movable portion pivotally attached thereto at a front portion of the base, with an extensible powered operator pivoting the chair with respect to the base at the hinge in order to lift the occupant forwardly and upwardly.
2. General Background
In the care of invalids, elderly, disabled and/or injured persons, there is commonly employed a chair having an occupant assisting feature in the form of a mechanical or electro-mechanical mechanism that powers the chair and/or the back portion of the chair upwardly and forwardly so as to assist the occupant in moving from a sitting to a standing position. Some "lift" chairs use mechanical mechanisms to operate the seat and back portions separately. This type of lift chair apparatus can be seen generally in the Gaffney U.S. Pat. Nos. 3,250,569; 4,007,960; and 4,083,599; as well as the Horstmann U.S. Pat. No. 3,851,917.
The prior art includes a number of mechanical devices in the form of lift chairs, chairs for invalids, reclining elevator chairs and the like. As an example, an early U.S. Pat. No. 3,147,038 issued to Varabas entitled "Reclining Chair" uses an electric motor to recline the back portion of a chair by swinging the chair to and from upright and reclining positions. The mechanism includes a pair of back rails and a sub-frame having portions engaging the outer faces of the rails and movable only in the plane of the rails. The sub-frame has an upholstered portion concealing the rails.
In the Gaffney U.S. Pat. No. 3,250,569 entitled "Elevator Seats" there is provided an improvement in elevator seats and particularly to a compact elevator seat unit having a low profile and adapted to be disposed between a seat cushion and a seat base of a chair. The lifting mechanism is designed to be contained between the base and the seat panels of the unit so that nothing projects outwardly of the unit. The unit is designed to fit into the seat base of any chair and beneath its cushion, thus to convert a conventional chair to an elevator chair. The Gaffney '569 patent is designed so that no part of the elevator chair unit needs be built into the chair. The device includes an electrical motor driving belts and sheaves as part of the power source of the operating mechanism.
The McKee U.S. Pat. No. 3,596,991 provides an arm chair including hydraulically controlled seat and arms whereby a forward and upward pivoting of the arms and seat can be effected so as to raise an occupant from the chair. Alternatively, the seat in conjunction with a supporting base and the back of the chair can pivot rearwardly so as to assume a partially reclining position with a footrest, through an appropriate linkage, extending to assume a leg supporting position.
The Hodge U.S. Pat. No. 3,640,566 entitled "Invalid Chair" provides a seat back hinged to the back of the seat and a lower frame hinged to the front of the seat to form an extensible assembly which is pivoted to a main support frame, the seat being spring loaded in a direction to extend the assembly of frames so that an invalid is assisted from the seat to his feet, the assembly also being positionable in a recumbent position so that the chair functions as a bed.
The Horstmann U.S. Pat. No. 3,851,917 is concerned with invalid chairs for facilitating standing up and sitting down operations by invalids who are normally unable to stand up and sit down without difficulty. The device comprises a chair base, a seat portion, a back rest, linkage interconnecting the chair base, seat portion and back rest, and resilient means to urge the seat portion and back rest to raised positions and thereby assist an occupant in rising from a sitting position. The back rest is connected to the chair base by a quadrilateral linkage including upper and lower links extending forward from the lower part of the back rest to pivots on the chair base, the seat portion being pivoted to the back rest or to the upper link in the vicinity of the junction therebetween and further linkage being provided whereby as the seat portion and back rest are raised by the resilient means, the seat portion pivots to an angular position where its forward end lies upwardly with respect to the upper link and the inclination between the seat portion and backrest is greater than the corresponding inclination with the seat fully forward.
In the Amstutz U.S. Pat. No. 3,881,771 there is provided a convertible chair that can be converted to various configurations by means of parallelogram linkage actuated by a crank which is in turn actuated by a screw operated by a belt and electric motor.
The Gaffney U.S. Pat. No. 4,007,960 provides a reclining elevator chair having a tiltable back, and extendible leg rest, and means for raising the seat and simultaneously titling it forwardly to assist arthritic or other partially disabled persons in leaving the chair. A power-driven ram tilts the back and extends and retracts the leg rest in one mode of operation. In a second mode of operation, the same ram raises the seat and tilts it forwardly. The first mode of operation occurs when the ram is extended beyond the predetermined length. When the ram is equal to the predetermined length, a portion of the mechanism which tilts the back and extends and retracts the leg rest abuts against a portion of the seat frame and transfers the force of the ram from the back and leg rest to the seat.
In the Gaffney U.S. Pat. No. 4,083,599, a lift chair provides a lift base, a seat, and an extensible and retractable power-actuated ram connected between the lift base and seat to selectively raise and lower the seat. One or another accessory base provided with accessories such as a rocker or wheel assembly is also connected to the seat and is positioned to contact the floor before the ram is fully retracted so that the full retraction of the ram lifts the lift base off the floor and transfers the entire weight of the chair to the accessory base. When the ram is extended, the initial extension of the ram reseats the lift base on the floor and lifts the accessory base off the floor, thus transferring the weight of the chair from the accessory base back to the lift base, which supports and stabilizes the chair during the lifting thereof and until the ram is fully retracted again.
All of these prior art, patented mechanisms provide relatively complex linkage between the seat base and the movable seat portion or sub-frame. These complicated mechanisms require high manufacturing costs and thus higher cost to the end user. Additionally, more complicated mechanisms create a potential for higher maintenance which usually accompanies greater complexity.
It is an object of the present invention to provide an elevator chair for invalids wherein a simplified, yet structurally sound and easily operable lift chair apparatus can be provided at lower expense to the end user as compared with comparable lift chairs having complex mechanical linkage.